Ask your friend or relative to sit in a straight backed chair with his or her knees pressed together, feet flat on the floor with his or her hands firmly gripping the side edges of the seat. Now stand in front of that person and place your middle finger in the middle of their forehead.
Next, breathe deeply and put on an act that you're focusing your mental energy upon on your chosen potential dupe. When you're ready, invite your mark to attempt to stand up. Just before the person stands up, explain to him/her that they will find it impossible to do so since you are using your psychic energy to keep them pinned to the chair.
The mark will not be able to stand up -no matter how hard they try.
The secret: In order for the person to stand up, he or she must move his center of gravity in front of his or her knees, but they won't be able to do that with their backside stuck at the back of the chair.
Sit on the floor with your legs crossed. Put your dominant hand on top of your head with the palm face down. Spread your fingers wide. Now ask a friend to grip your arm at the elbow and attempt to remove your hand from your head. They will find it almost impossible.
The secret: Your arm is a lever and the powerful parts of any lever are the ends. Your elbow is the fulcrum, so any attempt to exert force at this point will be easily matched by the leverage in your arm. Think of it like this: Trying to open a door by pressing on the hinges.
It's fun to fuck with people, isn't it? As long as they don't shoot you.